1. Field of Invention
This invention relates to constructional elements of L-shaped cross-section comprising two metal flanges joined together at right-angles each flange having at least one row of regularly spaced holes or apertures extending longitudinally thereof. Elements of this type cut to suitable lengths can be secured together by fixing means inserted through registering holes or apertures to form a variety of structural units and frameworks.
2. Description of Prior Art
Constructional elements of the type referred to above are described in the specifications of my two earlier British Pat. Nos. 696,531 and 856,780.
In my earlier British Pat. 696,531 I disclosed a constructional element of constant thickness and of L-shaped cross-section having a narrow flange and a wide flange, a row of holes extending longitudinally of the narrow flange, and two rows of holes extending longitudinally of the wide flange, the minimum distance between the adjacent edges of adjacent holes in each row being the same throughout each row, said distance being the same in the case of each of the three rows, the row of holes in the narrow flange and the two rows of holes in the wide flange being repetitions of one another and each consisting of a plurality of alternate round and elongated holes, the round holes all being of the same size, the elongated holes all being of the same diameter, said elongated holes being elongated transversely of the element, said elongated holes being of a width equal to the diameter of one of the round holes and of a length equal to the diameter of one of the round holes plus twice the thickness of the element, the round holes in any given row of holes being transversely aligned with the elongated holes in the next adjacent row of holes.
I later found that the element of my first mentioned patent could be rendered substantially more versatile by radically changing the number, shape, and arrangement of holes in the inner row of holes in the said wide flange; and in the L-shaped element disclosed in my later British Pat. No. 856,780 the said row consists of a plurality of holes which are alternately elongated transversely and longitudinally of the member, the transversely elongated holes being similar in size to the transversely elongated holes in the other two rows and the longitudinally elongated hole being of the same width as one of the round holes in the other two rows and of a length at least as great as the centre-to-centre distance between two of the transversely elongated holes in one of said other rows plus the diameter of one of said round holes.
I now find that the utility of such a constructional element can be further improved by altering the configuration of the holes or apertures to provide in each row a series of round holes alternating with holes which are elongated both in the longitudinal and transverse direction of the element.